Published U.S. Pat. Nos. 4,434,048 and 4,434,226 set forth tabular emulsions. These emulsions comprise greater than 70 percent projected area of tabular grains. Most of the conditions which promote tabularity also lead to grain growth and polydispersed size distribution.
Using solvent to give narrow size distribution is discussed in many photographic books, such as Photographic Emulsion Chemistry by G. F. Duffin, 1966, or Introduction to Photographic Theory by B. H. Carroll et al, 1980. In tabular grain, using a large amount of solvent such as U.S. Pat. No. 4,722,886--Nottorf discloses narrow tabular grain size distribution, but Nottorf's process also promotes tabular grain increase in diameter and thickness. It is very difficult to grow small diameter tabular grains with little fine grain contamination, narrow tabular grain size distribution, and also maintain a relatively large aspect ratio for the tabular grains when using a large amount of solvent. Fine grains as a contaminate absorb sensitizing dye and incoming light but form little image. The fine grains also include 3D grains which scatter light and degrade sharpness. It is very desirable to reduce the presence of fine grain.
There is a continuing need to improve forming of tabular silver halide grains. There is a particular need to form more monodispersed emulsions. This is particularly difficult with tabular grains of a small equivalent circular. It has been difficult to produce grains of an equivalent circular diameter of between 0.5 and 2 microns without having a high percentage of fines of less than this size. It is also difficult to form such small grains that are thin with a large aspect ratio. Formation of such small grains is of interest, as they have particular utility for the lower speed layers of color negative films.